Working Principles and Technical Analysis of TFT-LCD Liquid Crystal Displays
Optical Properties and Application Principles of Polarizers
Polarizers, as key optical components in liquid crystal displays (LCDs), operate based on the polarization characteristics of light. Light, being an electromagnetic wave, has its propagation direction perpendicular to the electric field and magnetic field components, forming transverse wave properties. In high school physics experiments, we have verified the wave nature of light through various experiments, with polarization phenomena being one of the most intuitive proofs.
The core function of a polarizer is similar to an optical barrier; it selectively allows light with specific polarization directions to pass through. Specifically, when natural light (which contains polarized light in all directions) strikes a polarizer, only those components aligned with the 'barrier' direction can pass through while others are blocked. This selective transmission significantly reduces the intensity of transmitted light—similar to wearing sunglasses.
When two polarizers are used together, more interesting optical phenomena occur. As the relative rotation angle between them changes, the transmitted intensity varies regularly. When their polarization directions are parallel, maximum transmission occurs; when they are perpendicular to each other, no light passes at all. This characteristic is cleverly applied in LCDs—by filling liquid crystal material between two orthogonal polarizers and controlling molecular orientation using an electric field for precise modulation of transmitted intensity.
Precision Structure of Glass Substrates and Alignment Films
The core structure of LCDs consists of two layers made from high-precision glass substrates that not only require extremely high flatness but also special surface treatment processes. The lower glass substrate integrates millions of thin-film transistors (TFTs) forming a matrix network for driving circuits; meanwhile, the upper layer features an array for color filters responsible for generating colors.
The surfaces where glass substrates contact liquid crystals aren't simple smooth planes but rather specially treated microstructures. Ideally these surfaces should possess regular serrated grooves which guide liquid crystal molecules into orderly arrangements along specific directions—a crucial factor for controlling light propagation direction since disordered arrangements lead to scattering effects causing leakage issues that severely impact display quality.
In actual production processes creating regular grooves directly on glass surfaces poses technical challenges. Modern manufacturing techniques utilize polyimide (PI) coatings instead as substitutes for physical grooves by applying PI materials onto glass surfaces followed by friction processing using fabrics oriented in specific directions ('rubbing process') so that molecules form directional alignments on PI's surface known as alignment films providing uniform arrangement benchmarks ensuring ordered molecular configurations according design requirements.
Twisted Nematic Liquid Crystals’ Torsional Arrangement Characteristics
TN (Twisted Nematic) type LCD technology was among earliest commercialized applications characterized primarily by 90-degree helical arrangement structures within liquid crystal molecules under unpowered states aligning naturally due differences orientations across top/bottom alignment films respectively exhibiting precise angular deviations around 90 degrees allowing gradual twisting effect from upper layer downwards throughout entire system facilitating ideal conditions whereby incident polarized lights rotate accordingly resulting optimal passage via both layers maintaining bright state displays upon successful interactions occurring therein; nUpon application voltage TN-type’s dielectric anisotropy begins influencing behavior whereupon preferentially aligned towards electrical fields thus leading transition spiral formations reverting vertical placements hindering further rotations hence blocking subsequent transmissions achieving dark state displays fundamental principles underlying TN technologies employed widely today . n n### Design Considerations Between Normally White & Normally Black Modes nLiquid Crystal Displays categorized initially depending respective default states either classified under normally white(NW)/normally black(NB ) modes determined chiefly contextual usage scenarios ; NW mode denotes panel remains transmissive without power supply(illuminated state ), conversely NB operates oppositely remaining opaque until activated externally turning illuminated subsequently activating brightness levels adjusted dynamically per situational demands involved during operations executed consistently over time enhancing overall performance metrics observed across varied environments encountered routinely . n nSuch selections derive mainly from practical application needs surrounding devices utilized e.g., computer monitors favoring NW mode suited predominantly given typical office settings wherein majority screen areas remain lit minimizing operational energy consumption thereby prolonging longevity lifespan attributed ultimately benefiting end-users greatly optimizing resource allocation strategies effectively implemented herein accordingly . n ...